Citrix has released an informative blog post in which they outline the differences between the Citrix XenApp and XenDesktop IMA and FMA architectures and also map all features of the old IMA architecture to the equivalent featuers of the new FMA architecture.
XenApp 6.5 has reached end of maintenance and with the end of life date only a few months away, migrating your existing 6.5 environment(s) to XenApp & XenDesktop 7 is highly recommended. This also means moving from the IMA architecture to FMA. In earlier 7.x versions, some 6.5/IMA features were not available, but rest assured, they were added throughout new releases. Because some features have been rebranded or have gone through some design changes and improvements, this blog article may assist you in finding the XenApp 6.5 feature you are looking for in XenApp & XenDesktop 7. The Citrix blog post provides a summary of all important XenApp 6.5 features and how they translate to the feature set of XenApp & XenDesktop 7: https://www.citrix.com/blogs/2018/04/06/from-ima-to-fma-where-to-find-xenapp-6-5-features-in-xenapp-xendesktop-7/
Further documentation can be found at: https://support.citrix.com/article/CTX201127
Another good IMA to FMA comparison is released by CTP Bas Van Kaam at: